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Biomolecules question

2021 · 25 Feb · Shift 1 · Q8
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Biomolecules question

2021 · 25 Feb · Shift 1 · Q8

JEE MainChemistryBiomoleculesMCQ+4 / −1
Which of the glycosidic linkage between galactose and glucose is present in lactose?
  1. A
    C-1 of galactose and C-6 of glucose
  2. B
    C-1 of glucose and C-6 of galactose
  3. C
    C-1 of galactose and C-4 of glucose
  4. D
    C-1 of glucose and C-4 of galactose
View written solutionFree

Correct answer: C

  1. Recall the structure of lactose

    Lactose is a disaccharide made of:

    • galactose
    • glucose

  2. Identify the glycosidic linkage in lactose

    In lactose, the glycosidic bond is formed between:

    • C-1 of β\betaβ-D-galactose
    • C-4 of D-glucose

    So, lactose has a β(1→4)\beta(1 \to 4)β(1→4) glycosidic linkage.

  3. Evaluate the options

    • A: C-1 of galactose and C-6 of glucose
      This corresponds to a (1→6)(1 \to 6)(1→6) linkage, so incorrect.

    • B: C-1 of glucose and C-6 of galactose
      Wrong sugars and wrong carbon positions, so incorrect.

    • C: C-1 of galactose and C-4 of glucose
      This matches the structure of lactose, so correct.

    • D: C-1 of glucose and C-4 of galactose
      This reverses the actual linkage, so incorrect.

  4. Final answer

    The glycosidic linkage present in lactose is between C-1 of galactose and C-4 of glucose.

    Therefore, the correct option is C.

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